The present invention relates to an illuminated vitrectomy probe or other illuminated ophthalmic surgical instrument, and more particularly to an optical fiber array configuration designed to provide illumination over a specific area at the working end of an instrument, for example, the cutting port of a vitrectomy probe.
Anatomically, the eye is divided into two distinct parts—the anterior segment and the posterior segment. The anterior segment includes the lens and extends from the outermost layer of the cornea (the corneal endothelium) to the posterior of the lens capsule. The posterior segment includes the portion of the eye behind the lens capsule. The posterior segment extends from the anterior hyaloid face to the retina, with which the posterior hyaloid face of the vitreous body is in direct contact. The posterior segment is much larger than the anterior segment.
The posterior segment includes the vitreous body—a clear, colorless, gel-like substance. It makes up approximately two-thirds of the eye's volume, giving it form and shape before birth. It is composed of 1% collagen and sodium hyaluronate and 99% water. The anterior boundary of the vitreous body is the anterior hyaloid face, which touches the posterior capsule of the lens, while the posterior hyaloid face forms its posterior boundary, and is in contact with the retina. The vitreous body is not free-flowing like the aqueous humor and has normal anatomic attachment sites. One of these sites is the vitreous base, which is a 3-4 mm wide band that overlies the ora serrata. The optic nerve head, macula lutea, and vascular arcade are also sites of attachment. The vitreous body's major functions are to hold the retina in place, maintain the integrity and shape of the globe, absorb shock due to movement, and to give support for the lens posteriorly. In contrast to aqueous humor, the vitreous body is not continuously replaced. The vitreous body becomes more fluid with age in a process known as syneresis. Syneresis results in shrinkage of the vitreous body, which can exert pressure or traction on its normal attachment sites. If enough traction is applied, the vitreous body may pull itself from its retinal attachment and create a retinal tear or hole.
Various surgical procedures, called vitreo-retinal procedures, are commonly performed in the posterior segment of the eye. Vitreo-retinal procedures are appropriate to treat many serious conditions of the posterior segment. Vitreo-retinal procedures treat conditions such as age-related macular degeneration (AMD), diabetic retinopathy and diabetic vitreous hemorrhage, macular hole, retinal detachment, epiretinal membrane, CMV retinitis, and many other ophthalmic conditions.
A surgeon performs vitreo-retinal procedures with a microscope and special lenses designed to provide a clear image of the posterior segment. Several tiny incisions just a millimeter or so in length are made on the sclera at the pars plana. The surgeon inserts microsurgical instruments through the incisions such as a fiber optic light source to illuminate inside the eye, an infusion line to maintain the eye's shape during surgery, and instruments to cut and remove the vitreous body (such as a vitrectomy probe—which has a cutting end that is inserted into the eye. A vitrectomy probe has a small gauge needle or cannula with a cutting mechanism on the end that is inserted into the eye).
During such surgical procedures, proper illumination of the inside of the eye is important. Typically, a thin optical fiber is inserted into the eye to provide the illumination. A light source, such as a metal halide lamp, a halogen lamp, a xenon lamp, or a mercury vapor lamp, is often used to produce the light carried by the optical fiber into the eye. The light passes through several optical elements (typically lenses, mirrors, and attenuators) and is launched at an optical fiber that carries the light into the eye.
To reduce the number of required incisions during vitrectomy surgery and improve the delivery of light to the surgical site, an effort has been made to integrate a light source (typically one or more optical fibers) with a vitrectomy probe. These efforts have been difficult because of the small diameters of vitrectomy probes. It is desirable to make the diameter of the cutting end of the vitrectomy probe as small as possible so that it can be inserted through very small incisions into the eye.
In one case, a ring of optical fibers is disposed around a vitrectomy probe and held in place by a sleeve. This illuminated vitrectomy sleeve consists of a bundle of small diameter optical fibers fed into a hub region and then distributed in a ring pattern. The illuminated vitrectomy sleeve is designed to be a stand-alone device into which the vitrectomy probe is inserted. As such, it must have its own structural strength that is provided by a sandwiching the array of optical fibers between two metal or plastic cylindrical cannulas. Since it is preferable to make the total diameter of the vitrectomy probe and sleeve as small as possible, very little cross-sectional area is left to house the optical fibers. Accordingly, very little light is transmitted into the eye. In addition, the ring of fibers distributes light throughput the entire region adjacent to the distal end of the vitrectomy probe instead of concentrating it on the cutting port opening where it is needed.
In another case, a single fiber may be attached to the vitrectomy needle and held in place with a plastic sleeve. For example, Synergetics, Inc. manufactures a 25 gauge vitrectomy needle with a single optical fiber that is held in place with a plastic sleeve. The plastic sleeve can then fit into a 20 gauge cannula that is inserted into the eye. Very little cross-sectional area is available between the 25 gauge vitrectomy needle and the inner surface of the plastic sleeve (which is typically one or two mils thick). In addition, a larger incision must be made to accommodate the 20 gauge cannula through which the plastic sleeve must fit. Today, it is preferable to keep the incision size small so as to accommodate a probe with a diameter of 23 gauge or smaller. What is needed is an improved illuminated vitrectomy probe that delivers sufficient light into the eye while accommodating these smaller incision sizes.
In addition, the same constraints restrict the feasible size of other ophthalmic surgical instruments. For example, scissors, forceps, aspiration probes, retinal picks, delamination spatulas, various cannulas, and the like may also benefit from targeted illumination. These instruments are designed to fit through small gauge cannulas that are inserted through the sclera during surgery. The same principles used to design an improved illuminated vitrectomy probe can also be used to provide targeted illumination for these other surgical instruments.